Quick Guide: 6 Reasons to keep your machining coolant clean

Whether you call it machine Coolant, Metalworking Fluid or ‘Suds’, there are obvious benefits of keeping this liquid clean. Clean machine coolant contributes to keeping your machines healthy and most machinists recognise it is the first step to getting more out of your machines for less.

To be frank, poorly maintained machining coolant stinks. But if the stench of rancid machine coolant isn’t enough to motivate you to change it, the impact on your health and the health of your machines really should.

That’s why below we’re highlighting 6 reasons to keep your machining coolant clean. We’ve also included pointers on optimizing coolant maintenance, which can increase productivity while helping to protect your shop’s most important assets: your workers…

•  Clean cutting fluid helps to create more lubrication between the tool and the workpiece. 
• This removes heat, reduces friction and wear on the cutting tools, prolonging their lifespan and reducing the frequency of tool replacements.
• As coolant breaks down, the sulfur, chlorine and other extreme-pressure compounds contained within become ineffective.
• Machine tool life suffers when concentration drops below the coolant manufacturer’s minimum concentration suggestions and can cause rust on the machine tool.
• This leads to poor tool and machine life as well as problems with accuracy and part quality, all of which increases the likelihood of part rejection, and the costs incurred.
• Longer tool life and less replacements on the other hand, means lower costs. 

• Clean cutting fluid maintains its chemical properties, providing consistent lubrication, which reduces heat generation and prevents damage to the tool and the workpiece.
• Preventing excess heat buildup also helps to avoid colour distortion of the workpiece material itself and avoiding any reduction in the quality of the workpiece.
• This is important when working with non-ferrous metals that have a lower melting point. Effective cooling also means the swarf and chips coming off the workpiece remains cool enough to avoid sticking to your tool.
• Contaminated cutting fluid can lead to staining, poor surface finishes and dimensional inaccuracies.
• Clean fluid that enables consistent cooling and lubrication therefore leads to higher-quality machined parts. 

• Clean cutting fluid prevents the build-up of debris and contaminants in the machine, which can cause pump blockages and damage to internal components. 
•  Cleaner machines mean improved machine performance and less downtime.
• Clean cutting fluid increases the efficiency of cooling and lubrication - reducing the load on your machine spindle.
• Your machine does not have to work so hard, meaning less energy is required for machining operations and lower costs.
•  It is a good idea to wipe equipment down before going home at the end of each shift. Regularly inspect seals and wipers for wear and replace as needed, especially in older machines.
• Install a skimmer on each machine to eliminate tramp oil, bacteria’s favourite food. Tramp oil will slowly dissolve into the coolant, causing it to get thicker and stickier with time

• Even freshly mixed cutting fluids contain a host of chemical additives such as biocides, emulsifiers, corrosion inhibitors and anti-foaming agents that may cause skin irritation, rashes and dermatitis.
• When cutting fluid is neglected, the concentration of these chemicals may reach unsafe conditions. 
• Coolant that is not well maintained gets contaminated. Contaminated cutting fluid can harbour harmful bacteria and fungi, posing health risks to workers through skin contact - including skin conditions such as dermatitis.
• Unmanaged coolant also increases ‘misting’, which is not always cleared by extraction units within the machine cabinet. Inhalation of mist by workers can cause occupational asthma.
• Also, enjoy working in an environment that smells like rotten eggs? No, us neither. Contaminated cutting fluid can produce this kind of unpleasant odour. Throwing in coolant mints may help to disguise the odour but is not a sustainable solution. Keep it clean instead.
• Proper maintenance of cutting fluids helps your company adhere to environmental regulations and standards by minimising hazardous waste, spills or leaks.
•  Clean fluid therefore maintains a safer working environment and reduces the risk of occupational illnesses.

•  ‘Tramp oil’ (fungus or bacteria) forming within your coolant can cause the coolant to become acidic.
• This will start to rust your sump, leading to costs of cleaning and repair.
• If this contaminates nearby waterways, it will result in significant Health, Safety and Environmental consequences. 
•  Clean cutting fluid therefore protects both the machine and the workpieces from corrosion, which can occur if the fluid becomes contaminated with water, dirt, or metal particles.

• We have already discussed how clean machining fluid leads to increased tool life with less tool replacements and a higher quality machined part.
• Add to this the fact that clean fluid lowers the likelihood of machine repairs and production delays.
• But well-maintained cutting fluid also reduces the need for frequent fluid replacement and disposal, so you’ll save on buying new fluid and managing waste.
• You’ll also need less additives such as anti-foaming, bactericide and fungicide. 
•  Buying cutting fluid and disposing of it after use are necessary expenses. Though these costs don’t compare to the expense of an idle CNC machine tool, it’s a good idea to maximize coolant life whenever possible.
• Machine shops with a few dozen machine tools might consider a centralized cutting fluid system. 
•  If this isn’t you, a coolant recycling center is probably your best bet. Use a shop vacuum or sump cleaner to bring old cutting fluid back to the reservoir for processing.
• Maintenance is key. Skim constantly, clean regularly and check religiously. Watch fluid concentrations, using no more concentrate than is necessary but without skimping.
•  As a rule, 10 percent is a good starting point for general-purpose work, although difficult materials such as titanium and superalloys may call for a slightly higher percentage, while aluminum generally cuts best with a leaner mix.